The TOF-PET technique is more widely used in clinical diagnosis to improve image quality. However, the TOF performance of a TOF-PET scanner may decline after usage of the TOF-PET scanner for a period of time. The TOF performance of the TOF-PET scanner may be assessed periodically or from time to time. According to existing techniques for assessing the TOF performance of a PET scanner, one or more images may be reconstructed and one or more correction operations such as a normalized correction, an attenuation correction, or a system dead time correction may be performed in the reconstruction process. Such techniques may be time-consuming and costly. Therefore, it is desirable to provide systems and methods for assessing the TOF performance of a PET scanner with improved efficiency.